High-frequency module and communication apparatus

ABSTRACT

A high-frequency module includes a plurality of filters, a switch that commonly connects a plurality of paths, and a low noise amplifier that amplifies a high-frequency signal input from the plurality of filters with the switch interposed therebetween, wherein paths in which first and second filters are respectively provided among the plurality of paths connect the respective filters and the switch without connecting impedance elements, and each of the first and second filters has an output impedance located in a matching region between a NF matching impedance at which an NF of the low noise amplifier is minimum and a gain matching impedance at which a gain of the low noise amplifier is maximum in its respective pass band thereof on a Smith chart.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2017-109028 filed on Jun. 1, 2017 and Japanese PatentApplication No. 2016-155022 filed on Aug. 5, 2016. The entire contentsof each application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a high-frequency module and acommunication apparatus that include a low noise amplifier.

2. Description of the Related Art

In a mobile communication terminal, an LNA (Low Noise Amplifier)generating less noise is used for a high-frequency module such as areception-system front end circuit which handles a minute high-frequencysignal in order to suppress deterioration in a NF (Noise Figure). Afilter is provided at a previous stage of the LNA so as to transmit adesired frequency band such as a reception band and remove unnecessaryfrequency components.

In the circuit configured as described above, a matching circuit isprovided between the filter and the LNA (for example, see JapaneseUnexamined Patent Application Publication No. 2006-333390). To bespecific, in this configuration, an output impedance of the filter isset to be different from a characteristic impedance intentionally andthe matching circuit causes the output impedance and an input impedanceof the filter to match with each other (impedance matching).

The mobile communication terminal in recent years is required to becompatible with so-called multiband communication in which one terminaldeals with a plurality of frequency bands. With this compatibility, thehigh-frequency module including the low noise amplifier is also requiredto be compatible with the multiband communication. However, when aplurality of filters having different pass bands are provided in orderto satisfy the requirement, matching circuits for the same number asthat of the plurality of filters need to be provided with theabove-described existing configuration. This configuration thereforeposes an impediment to reduction in the high-frequency module in size.

When a matching circuit common to the plurality of filters is providedor when no matching circuit is provided for size reduction, it isdifficult to perform impedance matching for the plurality of bandsconcurrently and characteristics can be deteriorated. To be specific,the high-frequency module including the low noise amplifier is requiredto increase a gain while suppressing deterioration in the NF. As for thelow noise amplifier, an impedance to achieve impedance matching(so-called gain matching) so as to provide a maximum gain of the lownoise amplifier and an impedance to achieve impedance matching(so-called noise matching) so as to provide a minimum NF of the lownoise amplifier are different from each other. Therefore, with theconfiguration including the matching circuit common to the plurality offilters or the configuration including no matching circuit, it isextremely difficult to achieve both of suppression of deterioration inthe NF and increase in the gain for the plurality of bands because offrequency characteristics and the like even when they can be achievedfor only one band.

SUMMARY OF THE INVENTION

Accordingly, preferred embodiments of the present invention providehigh-frequency modules and communication apparatuses that are capable ofincreasing a gain while suppressing deterioration in an NF, are reducedin size, and are compatible with multiple bands.

According to a preferred embodiment of the present invention, ahigh-frequency module includes a plurality of filters including firstand second filters with pass bands which are different from one another,a connection circuit that commonly connects a plurality of paths inwhich the plurality of filters are respectively provided, and a lownoise amplifier that is connected to the connection circuit, wherein inpaths in which the first and second filters are respectively providedamong the plurality of paths, the respective filters and the connectioncircuit are connected without connecting impedance elements, and each ofthe first and second filters has an output impedance located in amatching region between a noise figure matching impedance at which anoise figure of the low noise amplifier is minimum and a gain matchingimpedance at which a gain of the low noise amplifier is maximum in in apass band of each of the first and second filters on a Smith chart.

When each of the first and second filters has the above-described outputimpedance, the gain is increased while suppressing deterioration in theNF without connecting an impedance element in each of the paths in whichthe first and second filters are respectively provided. That is to say,balance between NF performance and gain performance is significantlyimproved or optimized without providing individual matching circuits forthe first and second filters, which pose an impediment to sizereduction. Accordingly, a high-frequency module that is capable ofincreasing the gain while suppressing the deterioration in the NF, isreduced in size, and is compatible with multiple bands is provided.

Furthermore, a high-frequency module according to a preferred embodimentof the present invention may further include a first impedanceadjustment circuit that is connected between the connection circuit andthe low noise amplifier, wherein the first impedance adjustment circuitadjusts a first impedance when a circuit portion in which the firstimpedance adjustment circuit is connected to the low noise amplifier isseen from output sides of the plurality of filters in the case in whichthe noise figure is minimum and the gain is maximum.

The first impedance is able to be adjusted without depending on an inputimpedance of the low noise amplifier by including the above-describedfirst impedance adjustment circuit. That is to say, the matching regionis able to be located at a position that is appropriate for the outputimpedances of the first and second filters without depending on theinput impedance of the low noise amplifier on the Smith chart. The inputimpedance of the low noise amplifier and the output impedances of thefirst and second filters are restricted by various specifications suchas the respective circuit configurations and materials and so on.Therefore, the degree of freedom of design of the low noise amplifierand the first and second filters is able to be enhanced by providing thefirst impedance adjustment circuit.

The first impedance adjustment circuit may adjust the first impedance tobe any one of inductive or capacitive in both of the pass bands of thefirst filter and the second filter among the plurality of filters in thecase in which the noise figure is minimum and the gain is maximum.

The matching region is able to be located in one of inductive andcapacitive sides on the Smith chart by adjusting the first impedance tobe the other of inductive or capacitive in both of the pass bands of thefirst filter and the second filter as described above. The first andsecond filters having the configurations in which properties ofimaginary components of the output impedances are the same are thereforeable to be used.

Furthermore, each of the first and second filters may have the outputimpedance with a capacitive property in the respective pass band of eachof the first and second filters, and the first impedance adjustmentcircuit may adjust the first impedance to be inductive in both of thepass bands of the first filter and the second filter among the pluralityof filters in the case in which the noise figure is minimum and the gainis maximum.

The matching region and the output impedances are able to be made closeto each other by adjusting the first impedance to be inductive asdescribed above. Moreover, the NF matching impedance and the gainmatching impedance are able to be made close to each other, thus furtherincreasing the gain while further suppressing the deterioration in theNF.

The high-frequency module may further include a functional circuit thatis connected between a third filter of the plurality of filters and theconnection circuit and is structured and configured to perform apredetermined function.

A required function is able to be added to only a specific band assignedto a pass band of the third filter among the plurality of bands withwhich the high-frequency module is compatible by providing theabove-described functional circuit.

Furthermore, the functional circuit may be a second impedance adjustmentcircuit that generates a second impedance when a circuit portion inwhich the functional circuit is connected to the third filter is seenfrom an input side of the low noise amplifier close to the matchingregion in a pass band of the third filter on the Smith chart.

By including the second impedance adjustment circuit as the functionalcircuit, the balance between the NF performance and the gain performanceis able to be significantly improved or optimized for each of the firstto third filters even when frequency intervals of the pass band of thethird filter and the pass bands of the first and second filters arelargely separated from each other. Therefore, the plurality of bandswith which the high-frequency module is compatible are able to befurther widened.

The plurality of filters may include three or more filters, and each ofthe filters and the connection circuit may be connected withoutconnecting an impedance element in each of the plurality of paths.

With this configuration, a high-frequency module that is capable ofincreasing the gain while suppressing the deterioration in the NF, isreduced in size, and is compatible with multiple bands of three or morebands is able to be provided.

The connection circuit may be a switch element including a plurality ofselection terminals connected to the plurality of filters in anindividual correspondence manner and a common terminal connected to thelow noise amplifier.

By configuring the connection circuit by the switch element as describedabove, when only any one of the plurality of selection terminals isconnected to the common terminal, the plurality of paths in which theplurality of filters are provided are not connected to one another. Thisstructure and configuration therefore enhances isolation among theplurality of filters.

The connection circuit may include a multiplexer including a firstterminal connected to the low noise amplifier and a plurality of secondterminals connected to the plurality of filters in an individualcorrespondence manner.

By configuring the connection circuit to include the multiplexer asdescribed above, two or more high-frequency signals after passingthrough two or more filters among the plurality of filters are able tobe transmitted simultaneously. Therefore, the high-frequency module isable to be applied to CA (Carrier Aggregation) in which transmission andreception are performed using two or more bands among the plurality ofbands simultaneously.

In general, insertion loss of the multiplexer is lower than that of theswitch. Therefore, according to various preferred embodiments of thepresent invention, the gain is able to be further increased whilefurther suppressing the deterioration in the NF for the overallhigh-frequency module in comparison with the configuration in which theswitch is provided as the connection circuit.

The plurality of filters may include four or more filters, and theconnection circuit may include a first initial stage connection circuitthat commonly connects some paths among the plurality of paths, a secondinitial stage connection circuit that commonly connects at least twopaths which are different from the some paths among the plurality ofpaths, and a posterior stage connection circuit that is connected in amultistage structure to the first and second initial stage connectioncircuits.

The configuration of the connection circuit in which the circuits areconnected in a multistage arrangement as described above enhanceisolation among the plurality of filters.

The connection circuit may further include a third impedance adjustmentcircuit that is connected between the first initial stage connectioncircuit and the posterior stage connection circuit and generates a thirdimpedance when a circuit portion in which the third impedance adjustmentcircuit is connected to the first initial stage connection circuit isseen from an input side of the low noise amplifier close to the matchingregion in pass bands of some filters provided in the some paths amongthe plurality of filters on the Smith chart.

Frequency bands of bands assigned to the some filters provided in thesome paths that are commonly connected by the first initial stageconnection circuit among the plurality of bands with which thehigh-frequency module is compatible are referred to as a first frequencyband. Frequency bands of bands assigned to at least two filters providedin the at least two paths that are commonly connected by the secondinitial stage connection circuit among the plurality of bands with whichthe high-frequency module is compatible are referred to as a secondfrequency band.

When the connection circuit includes the third impedance adjustmentcircuit as described above, the balance between the NF performance andthe gain performance is able to be optimized for each of theabove-described some filters and the above-described at least twofilters even when the frequency intervals of the first frequency bandand the second frequency band are largely separated from each other.Therefore, the high-frequency module is able to be compatible with alarge number of bands having largely different frequencies in theplurality of bands with which the high-frequency module is compatible.The bands having the largely different frequencies indicate bands thefrequencies of which are largely different, such as an HB(High-Frequency) band (for example, band of about 2.5 GHz) and an MB(Medium-Frequency) band (for example, band of about 1800 MHz).

The posterior stage connection circuit may include a branch portionbranching a path connected to an input terminal of the low noiseamplifier into a path connected to a common terminal of the firstinitial stage connection circuit and a path connected to a commonterminal of the second initial stage connection circuit.

The high-frequency module is able to have the simplified configurationby providing the posterior stage connection circuit with the branchportion.

Each of the plurality of filters may include an elastic wave resonatorusing surface acoustic waves, bulk waves, or boundary acoustic waves.

The high-frequency module is able to be further reduced in size becausethe plurality of filters include the elastic wave resonators and arethus reduced in size. The plurality of filters are configured by theelastic wave resonators having generally high Q characteristics, thusreducing losses of the plurality of filters. Accordingly, the gain isincreased while suppressing the deterioration in the NF for the overallhigh-frequency module.

A communication apparatus according to another preferred embodiment ofthe present invention includes an RF signal processing circuit thatprocesses a high-frequency signal which is transmitted and received withan antenna element, and the high-frequency module according to any oneof the above-described preferred embodiments of the present inventionthat transmits the high-frequency signal between the antenna element andthe RF signal processing circuit.

With this configuration, communication apparatuses that are capable ofincreasing the gain while suppressing the deterioration in the NF, arereduced in size, and are compatible with multiple bands are able to beprovided.

The above and other features, elements, characteristics and advantagesof the present invention will become more apparent from the followingdetailed description of preferred embodiments of the present inventionwith reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit configuration diagram of a high-frequency moduleaccording to a preferred embodiment of the present invention.

FIG. 2 is a Smith chart illustrating positions defining outputimpedances of filters in a preferred embodiment of the presentinvention.

FIGS. 3A to 3C illustrate Smith charts for explaining an NF matchingimpedance and a gain matching impedance.

FIG. 4 is a Smith chart illustrating the output impedance of the filterwhen focusing on one band in a preferred embodiment of the presentinvention.

FIG. 5 is a circuit configuration diagram of a high-frequency moduleaccording to a first variation of a preferred embodiment of the presentinvention.

FIG. 6A is a circuit configuration diagram of a high-frequency moduleaccording to a first example of a second variation of a preferredembodiment of the present invention.

FIG. 6B is a circuit configuration diagram of a high-frequency moduleaccording to a second example of the second variation of a preferredembodiment of the present invention.

FIG. 6C is a circuit configuration diagram of a high-frequency moduleaccording to a third example of the second variation of a preferredembodiment of the present invention.

FIG. 7 is a circuit configuration diagram of a high-frequency moduleaccording to a third variation of a preferred embodiment of the presentinvention.

FIG. 8 is a circuit configuration diagram of a high-frequency moduleaccording to a fourth variation of a preferred embodiment of the presentinvention.

FIG. 9 is a circuit configuration diagram of a high-frequency moduleaccording to a fifth variation of a preferred embodiment of the presentinvention.

FIG. 10 is a circuit configuration diagram of a high-frequency moduleaccording to a sixth variation of a preferred embodiment of the presentinvention.

FIG. 11 is a circuit configuration diagram of a high-frequency moduleaccording to a seventh variation of a preferred embodiment of thepresent invention.

FIG. 12 is a circuit configuration diagram of a high-frequency moduleaccording to an eighth variation of a preferred embodiment of thepresent invention.

FIG. 13A is a circuit configuration diagram of a high-frequency moduleaccording to a first example of a ninth variation of a preferredembodiment of the present invention.

FIG. 13B is a circuit configuration diagram of a high-frequency moduleaccording to a second example of the ninth variation of a preferredembodiment of the present invention.

FIG. 13C is a circuit configuration diagram of a high-frequency moduleaccording to a third example of the ninth variation of a preferredembodiment of the present invention.

FIG. 14 is a circuit configuration diagram of a high-frequency moduleaccording to a tenth variation of a preferred embodiment of the presentinvention.

FIG. 15 is a circuit configuration diagram of a high-frequency moduleaccording to an eleventh variation of a preferred embodiment of thepresent invention.

FIG. 16A is an example of an impedance adjustment circuit in theeleventh variation of a preferred embodiment of the present invention.

FIG. 16B is another example of the impedance adjustment circuit in theeleventh variation of a preferred embodiment of the present invention.

FIG. 16C is still another example of the impedance adjustment circuit inthe eleventh variation of a preferred embodiment of the presentinvention.

FIG. 16D is still another example of the impedance adjustment circuit inthe eleventh variation of a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention andvariations thereof will be described in detail with reference to thedrawings. It should be noted that all of the preferred embodiments andvariations which will be described below indicate comprehensive orspecific examples. Numerical values, shapes, materials, components,arrangement and connection forms of the components, and the like whichwill be described in the following preferred embodiments and variationsare examples and are not intended to limit the present invention.Components that are not described in independent claims among thecomponents in the following preferred embodiments and variations aredescribed as arbitrary components. The sizes or the size ratios of thecomponents illustrated in the drawings are not necessarily strict orlimited.

FIG. 1 is a circuit configuration diagram of a high-frequency module 1according to a preferred embodiment of the present invention. FIG. 1also illustrates an RF signal processing circuit (RFIC (Radio FrequencyIntegrated Circuit)) 3 configuring a communication apparatus 4 togetherwith the high-frequency module 1.

The RFIC 3 is an RF signal processing circuit that processes ahigh-frequency signal which is transmitted and received with an antennaelement (not illustrated). To be specific, the RFIC 3 performs signalprocessing on the high-frequency signal (in this example, ahigh-frequency reception signal) input from the antenna element with thehigh-frequency module 1 interposed therebetween by down conversion orthe like, and outputs a reception signal generated by the signalprocessing to a baseband signal processing circuit (not illustrated).

In the present preferred embodiment, the RFIC 3 also is configured orprogrammed to function as a controller that controls connection of aswitch 20 (which will be described later) included in the high-frequencymodule 1 based on a frequency band to be used. To be specific, the RFIC3 switches a selection terminal that is connected to a common terminalfor the switch 20 with a control signal (not illustrated). Thecontroller may be provided at the outside of the RFIC 3 or may beprovided in, for example, the high-frequency module 1 or the basebandsignal processing circuit (not illustrated).

Next, the detail configuration of the high-frequency module 1 will bedescribed.

As illustrated in FIG. 1, the high-frequency module 1 includes aplurality of filters (three filters 10A to 10C in the present preferredembodiment), a connection circuit (switch 20 in the present preferredembodiment), an impedance adjustment circuit 30 (first impedanceadjustment circuit), and a low noise amplifier 40.

The filters 10A to 10C are, for example, bandpass filters having passbands which are different from one another. To be specific, Band A isassigned to the filter 10A, Band B is assigned to the filter 10B, andBand C is assigned to the filter 10C as the pass bands.

In the present preferred embodiment, the filters 10A to 10C have outputimpedances with capacitive properties in their respective pass bands. Tobe specific, each of the filters 10A to 10C preferably includes anelastic wave resonator using surface acoustic waves.

It should be noted that the elastic wave resonator may be a SAW (SurfaceAcoustic Wave) resonator, for example.

When the SAW resonator is used, it preferably includes a substrate andIDT (Interdigital transducer) electrodes. The substrate haspiezoelectricity on at least the surface thereof. For example, thesubstrate may include a multilayer body including a piezoelectric thinfilm on the surface thereof, a film with an acoustic speed which isdifferent from that of the piezoelectric film, a support substrate, andthe like. The overall substrate may have piezoelectricity. In this case,the substrate is a piezoelectric substrate defined by one layer of apiezoelectric body, for example.

It should be noted that the filters 10A to 10C are not limited to thebandpass filters and may be high pass filters or low pass filters.Furthermore, the number of filters is not limited to the above-describednumber and, for example, may be two or four or more. Each of the filters10A to 10C is not limited to have the above-described configuration andmay be configured by an elastic wave resonator using bulk waves orboundary acoustic waves.

The switch 20 is the connection circuit that commonly connects aplurality of paths in which the plurality of filters are provided (inthe present preferred embodiment, three paths 10 a to 10 c in which thethree filters 10A to 10C are respectively provided). In the presentpreferred embodiment, the three paths 10 a to 10 c in which the threefilters 10A to 10C are respectively provided connect the respectivefilters and the switch 20 without connecting impedance elements (forexample, inductors, capacitors, or the like).

To be specific, the switch 20 preferably is an SPnT (Single Pole nThrow)-type (n is the number of filters and three in the presentpreferred embodiment) switch element including a plurality of selectionterminals connected to the plurality of filters 10A to 10C in anindividual correspondence manner and a common terminal connected to thelow noise amplifier 40. In the present preferred embodiment, the commonterminal of the switch 20 is connected to the low noise amplifier 40with the impedance adjustment circuit 30 interposed therebetween.

The impedance adjustment circuit 30 is the first impedance adjustmentcircuit that is connected between the connection circuit (switch 20 inthe preferred embodiment) and the low noise amplifier 40. The impedanceadjustment circuit 30 adjusts an impedance Z (LNAin+ADJ) (firstimpedance) when a circuit portion in which the impedance adjustmentcircuit 30 is connected to the low noise amplifier 40 is seen from theoutput sides of the filters 10A to 10C to thus adjust an impedance Z(LNAin+ADJ_A), an impedance Z (LNAin+ADJ_B), and an impedance Z(LNAin+ADJ_C). That is to say, the impedance when the low noiseamplifier 40 is seen from the output sides of the filters 10A to 10C isadjusted to the impedance Z (LNAin+ADJ_A), the impedance Z(LNAin+ADJ_B), and the impedance Z (LNAin+ADJ_C) from an impedance Z(LNAin) (that is, an input impedance of the low noise amplifier 40) inthe case of providing no impedance adjustment circuit 30.

The impedance Z (LNAin+ADJ_A), the impedance Z (LNAin+ADJ_B), and theimpedance Z (LNAin+ADJ_C) are the impedances in the pass bands of thefilters 10A to 10C when the low noise amplifier 40 is seen from thefilters 10A to 10C, respectively.

The impedance adjustment circuit 30 preferably includes, for example, aninductor connected in series to a path connecting an input terminal andan output terminal. The configuration of the impedance adjustmentcircuit 30 is not limited thereto and it is sufficient that theimpedance adjustment circuit 30 includes an impedance element connectedto the path. To be specific, the impedance adjustment circuit 30 mayinclude an inductor or a capacitor connected in series to the pathconnecting the input terminal and the output terminal or an inductor ora capacitor connected in series to a path connecting the path and theground. It is sufficient that the circuit configuration of the impedanceadjustment circuit 30 and a constant of the impedance element areappropriately determined in consideration of impedance adjustmentrequired to be performed by the impedance adjustment circuit 30 based onthe input impedance L(LNAin) of the low noise amplifier 40 and outputimpedances Z (Fout_A) to Z (Fout_C) of the filters 10A to 10C.

The low noise amplifier 40 is a low noise amplifier circuit thatamplifies high-frequency signals input from the plurality of filters(for example, three filters 10A to 10C in the present preferredembodiment) with the connection circuit (switch 20 in the presentpreferred embodiment) interposed therebetween, and includes a transistoror the like.

In the high-frequency module 1 configured as described above, theplurality of paths 10 a to 10 c are bundled without connecting impedanceelements, thus reducing the high-frequency module in size and making itbe compatible with multiple bands.

In general, in a high-frequency circuit (distribution constant circuit),loss and the like are generated and an NF is deteriorated depending onan impedance relationship between connected circuits (for example,filters, LNA, and the like). All of the loss, the NF, and the like arefactors deteriorating the characteristics of the overall high-frequencycircuit. For this reason, when the high-frequency circuit is designed,impedance matching to adjust the impedance relationship between theconnected circuits is required.

As for the low noise amplifier 40, an NF matching impedance as animpedance to achieve impedance matching (NF matching) so as to provide aminimum NF of the low noise amplifier and a gain matching impedance asan impedance to achieve impedance matching (gain matching) so as toprovide a maximum gain of the low noise amplifier 40 are different fromeach other.

Therefore, when, for example, the NF matching for the low noiseamplifier 40 is performed in order to improve the NF, reflection by thelow noise amplifier 40 is increased due to deterioration in the gainmatching. In this case, loss of the circuit (filters 10A to 10C, and thelike) at the previous stage of the low noise amplifier 40 is increased,which leads to deterioration in the NF of the overall high-frequencymodule 1. On the other hand, when the gain matching for the low noiseamplifier 40 is performed in order to improve the gain performance ofthe low noise amplifier 40, the NF of the low noise amplifier 40 isdeteriorated due to deterioration in the NF matching. Even this casealso leads to the deterioration in the NF of the overall high-frequencymodule 1.

Accordingly, in order to increase the gain while suppressing thedeterioration in the NF of the overall high-frequency module 1, theimpedances (the output impedances of the filters 10A to 10C in thepresent preferred embodiment) when the circuit at the previous stage isseen from the low noise amplifier 40 need to be set between the NFmatching impedance at which the NF of the low noise amplifier 40 isminimum and the gain matching impedance at which the gain of the lownoise amplifier 40 is maximum.

FIG. 2 is a Smith chart illustrating positions defining the outputimpedances of the filters 10A to 10C in the present preferredembodiment.

As illustrated in FIG. 2, each of the filters 10A to 10C has the outputimpedance located in a matching region between the NF matching impedanceat which the NF of the low noise amplifier 40 is minimum and the gainmatching impedance at which the gain of the low noise amplifier 40 ismaximum in its respective pass band on the Smith chart.

To be specific, each of the NF matching impedance and the gain matchingimpedance has frequency characteristics and therefore draws a trajectoryas indicated by a bold line on the Smith chart. Therefore, for example,the filter 10A has the output impedance located between the NF matchingimpedance in Band A and the gain matching impedance in Band A on theSmith chart. It should be noted that the filters 10B and 10C have thesimilar output impedances except the point that the pass bands thereofare different from that of the filter 10A.

The impedance adjustment circuit 30 is provided between the connectioncircuit (switch 20) and the low noise amplifier 40 in the presentpreferred embodiment. The NF of the low noise amplifier 40 is minimumand the gain thereof is maximum at the NF matching impedance and thegain matching impedance illustrated in FIG. 2, respectively. Therefore,the circuit configuration (filters 10A to 10C in the preferredembodiment) connected to the low noise amplifier 40 with the impedanceadjustment circuit 30 interposed therebetween is required to providethese impedances.

This will be explained with reference to FIGS. 3A to 3C.

FIGS. 3A to 3C are Smith charts for explaining the NF matching impedanceand the gain matching impedance. To be specific, FIG. 3A is the Smithchart illustrating the impedance (impedance “NF_min_A” in FIG. 3A) atwhich the NF is minimum and the impedance (impedance “Gain_max_A” inFIG. 3A) at which the gain is maximum when the low noise amplifier 40 isseen from the output side of the filter 10A and illustrating theimpedance (impedance “NF_min_B” in FIG. 3A) at which the NF is minimumand the impedance (impedance “Gain_max_B” in FIG. 3A) at which the gainis maximum when the low noise amplifier 40 is seen from the output sideof the filter 10B. FIG. 3B is the Smith chart illustrating theabove-described four impedances when the circuit portion in which theimpedance adjustment circuit 30 is connected to the low noise amplifier40 is seen from the output sides of the filters 10A and 10B. FIG. 3C isthe Smith chart illustrating impedances (that is, impedances at whichmatching is optimum) matching with the respective four impedancesillustrated in FIG. 3B.

It should be noted that FIGS. 3A to 3C illustrate the impedances whilefocusing on the two frequencies for simple explanation. Hereinafter, theconnection circuit (switch 20 in the present preferred embodiment) ishandled as an ideal circuit in which the impedance is not changedbetween the input and output sides and wirings connecting the circuitsare handled as ideal wirings having electric lengths of zero fordescription. Practical circuit design should be made in consideration ofvariations in the impedance and a phase with the above-describedconnection circuit and wirings.

As illustrated in FIGS. 3A and 3B, the impedances (“NF_min_A” and“NF_min_B” in FIG. 3A) at which the NF is minimum and the impedances(“Gain_max_A” and “Gain_max_B” in FIG. 3A) at which the gain is maximumshift with the impedance adjustment circuit 30. In this case, impedancechange to FIG. 3B from FIG. 3A is defined by the circuit configurationof the impedance adjustment circuit 30 and the constant of the impedanceelement. The impedance change when the inductor as the impedanceadjustment circuit 30 is connected in series to the path connecting theinput terminal and the output terminal is illustrated in FIGS. 3A and3B.

To be specific, the impedance adjustment circuit 30 adjusts at least twoof the impedance Z (LNAin+ADJ_A), the impedance Z (LNAin+ADJ_B), and theimpedance Z (LNAin+ADJ_C) to be any one of inductive or capacitive inthe case in which the NF is minimum and the gain is maximum. In thepresent preferred embodiment, as illustrated in FIG. 3B, the impedanceadjustment circuit 30 adjusts the impedance Z (LNAin+ADJ_A) and theimpedance Z (LNAin+ADJ_B) in the pass bands of the plurality of filters10A and 10B to be inductive.

When the impedance Z (LNAin+ADJ_A) and the impedance Z (LNAin+ADJ_B) atwhich the NF is minimum and those at which the gain is maximum arelocated as illustrated in FIG. 3B, the impedances matching therewith aresubstantially complex conjugate impedances of the impedances illustratedin FIG. 3B, as illustrated in FIG. 3C.

That is to say, when the output impedance Z (Fout_A) of the filter 10Ahas the output impedance (NF matching impedance) indicated by “NF_min_A”in FIG. 3C, the NF of the low noise amplifier 40 is minimum. On theother hand, when the output impedance Z (Fout_A) has the outputimpedance (gain matching impedance) indicated by “Gain_max_A” in FIG.3C, the gain of the low noise amplifier 40 is maximum.

In the same manner, when the output impedance Z (Fout_B) of the filter10B has the output impedance (NF matching impedance) indicated by“NF_min_B” in FIG. 3C, the NF of the low noise amplifier 40 is minimum.On the other hand, when the output impedance Z (Fout_B) has the outputimpedance (gain matching impedance) indicated by “Gain_max_B” in FIG.3C, the gain of the low noise amplifier 40 is maximum.

As described above, the positions of the impedances at which the NF isminimum and the positions of the impedances at which the gain ismaximum, which are illustrated in FIG. 3C, are defined by FIG. 3B. Thatis to say, the impedance adjustment circuit 30 adjusts these positions.In other words, the impedance adjustment circuit 30 is able to adjustthe position of the matching region between the NF matching impedanceand the gain matching impedance on the Smith chart. Accordingly, theimpedance adjustment circuit 30 adjusts the matching region to a regionin which the output impedances Z (Fout_A) to Z (Fout_C) of the pluralityof filters 10A to 10C are easy to be located, thus increasing the gainwhile suppressing the deterioration in the NF for the plurality ofbands.

It is sufficient that at least two of the output impedances Z (Fout_A)to Z (Fout_C) of the filters 10A to 10C are located in the matchingregion in their respective pass bands. That is to say, this requirementis satisfied by not only the case in which the output impedances in onlya portion of their respective pass bands are located in the matchingregion but also the case in which the output impedances in theirrespective pass bands overall are located in the matching region. When,for example, one or more band(s) is(are) assigned to the pass bands ofthe filters 10A to 10C, the output impedances Z (Fout_A) to Z (Fout_C)of the filters 10A to 10C may be located in the matching region at anarbitrary frequency in one band of the one or more band(s) assigned totheir respective pass bands.

FIG. 4 is the Smith chart illustrating the output impedance Z (Fout) ofthe filter (any one of the filters 10A to 10C) when focusing on one bandin the present preferred embodiment. FIG. 4 also illustrates NF circles(equivalent NF circles) and gain circles (equivalent gain circles) atthe center frequency in the above-described band when the filter side isseen from the output side of the filter. To be specific, the NF circleindicates the output impedances of the filter with which the low noiseamplifier 40 has an equivalent NF and the gain circle indicates theoutput impedances of the filter with which the low noise amplifier 40has an equivalent gain.

As illustrated in FIG. 4, the output impedance Z (Fout) in one banddraws a trajectory from a frequency at a low-frequency edge of the bandto a frequency at a high-frequency edge thereof on the Smith chart. Thetrajectory is located in the matching region between a center point ofthe NF circles (that is, NF matching impedance) and a center point ofthe gain circles (that is, gain matching impedance). In other words, thetrajectory of the impedance in the band intersects with a lineconnecting the center point of the NF circles and the center point ofthe gain circles.

Hereinafter, advantageous effects that are provided by thehigh-frequency module 1 in the present preferred embodiment aredescribed while including circumstances which have derived the preferredembodiments of the present invention.

In general, as the high-frequency module satisfying a requirement forsize reduction and compatibility with multiple bands, the configurationin which an LNA is provided commonly to a plurality of filters can beconsidered. However, when filters designed in a common 50Ωsystem areused, a plurality of matching circuits need to be individually providedat the subsequent stages of the plurality of filters in order to satisfyoptimum design to increase a gain while suppressing deterioration in anNF. The high-frequency module configured as described above can howeverdeteriorate the NF of the overall high-frequency module due to anincrease in loss, pose an impediment to size reduction due to increasein the number of components, and so on.

Furthermore, as the high-frequency module satisfying the above-describedrequirement, the configuration in which not only the LNA but also thematching circuit is commonly provided is considered. It is howeverdifficult to satisfy the above-described optimum design for all of thebands when the filters designed in the common 50Ωsystem are used becauseboth of a matching impedance at which the NF of the LNA is minimum and amatching impedance at which the gain of the LNA is maximum havefrequency characteristics. To be specific, when the high-frequencymodule is configured so as to satisfy the above-described optimum designfor one band, the NF is deteriorated or the gain is lowered for theother bands. For this reason, it is difficult to sufficiently bring outgain performance and NF performance of the LNA for the other bands.

Meanwhile, as the high-frequency module satisfying the above-describedoptimum design for all of the bands, the configuration in which thematching circuits and the LNAs are provided in an individualcorrespondence manner to the plurality of filters can be considered.This configuration however increases a circuit scale due to increase inthe number of components of the matching circuits and the LNAs and hasdifficulty in reducing the size and cost. Moreover, fluctuation inquality among the high-frequency modules is easy to occur.

To cope with these circumstances, the present inventor has discoveredthe configuration of the high-frequency module 1 that satisfies theoptimum design to increase the gain while suppressing the deteriorationin the NF, is capable of being reduced in size, and is compatible withmultiple bands by using the plurality of filters (for example, threefilters 10A to 10C in the present preferred embodiment) with adjusted(customized) output impedances. A method to adjust the output impedancesof the filters 10A to 10C is not particularly limited but examplesthereof include the following. To be specific, when each filter is asurface acoustic wave filter configured by a plurality of IDT(InterDigital Transducer) electrodes, the output impedance is adjustedby making electrode parameters such as a pitch of electrode fingers, anintersecting width, the number of pairs of electrode fingers, and aninterval between reflectors and the IDT electrode of the IDT electrodedifferent among the IDT electrodes. When each filter includesladder-type elastic wave resonators, the output impedance is adjusted bymaking the impedance of the elastic wave resonator arranged at theclosest position to an output terminal of the filter be higher or lowerthan those of the other elastic wave resonators.

That is to say, with the high-frequency module 1 in the presentpreferred embodiment, first and second filters (any two filters of thefilters 10A to 10C in the preferred embodiment) have the outputimpedances located in the matching region between the NF matchingimpedance and the gain matching impedance (see FIG. 2). With this, thegain is increased while suppressing the deterioration in the NF withoutconnecting impedance elements in the paths in which the first and secondfilters are provided. That is to say, balance between the NF performanceand the gain performance is able to be optimized without providingindividual matching circuits for the first and second filters, whichpose an impediment to size reduction. Accordingly, the high-frequencymodule 1 that is capable of increasing the gain while suppressing thedeterioration in the NF, is reduced in size, and is compatible with themultiple bands is able to be provided.

In particular, the high-frequency module 1 in the present preferredembodiment includes three or more (for example, three in the presentpreferred embodiment) filters 10A to 10C and each of the plurality ofpaths 10 a to 10 c connects each of the filters and the connectioncircuit (switch 20 in the present preferred embodiment) withoutconnecting impedance elements. With this configuration, thehigh-frequency module 1 that is capable of increasing the gain whilesuppressing the deterioration in the NF, is reduced in size, and iscompatible with the multiple bands of three or more bands is able to beprovided.

The high-frequency module 1 in the present preferred embodiment includesthe impedance adjustment circuit 30 (first impedance adjustmentcircuit). With the impedance adjustment circuit 30, the impedance Z(LNAin+ADJ) (first impedance) when the circuit portion in which theimpedance adjustment circuit 30 is connected to the low noise amplifier40 is seen from the output sides of the plurality of filters 10A to 10Ccan be adjusted without depending on the input impedance Z (LNAin) ofthe low noise amplifier 40. Therefore, the impedance Z (LNAin+ADJ_A),the impedance Z (LNAin+ADJ_B), and the impedance Z (LNAin+ADJ_C) of therespective paths 10 a to 10 c when the low noise amplifier 40 is seenfrom the respective filters 10A to 10C can be adjusted. That is to say,the matching region is able to be located at a position that isappropriate for the output impedances of the first and second filterswithout depending on the input impedance Z (LNAin) of the low noiseamplifier 40 on the Smith chart. The input impedance Z (LNAin) of thelow noise amplifier 40 and the output impedances of the first and secondfilters are restricted by various specifications such as the respectivecircuit configurations and materials and so on. Therefore, the degree offreedom of design of the low noise amplifier 40 and the first and secondfilters is enhanced by providing the impedance adjustment circuit 30.

To be specific, with the high-frequency module 1 in the presentpreferred embodiment, at least two impedances of the impedances (Z(LNAin+ADJ_A), Z (LNAin+ADJ_B), and Z (LNAin+ADJ_C)) of the respectivepaths 10 a to 10 c when the low noise amplifier 40 is seen from therespective filters 10A to 10C are adjusted to be one of inductive orcapacitive in both of the pass bands thereof, thus locating the matchingregion in the other of inductive and capacitive sides on the Smithchart. The first and second filters having the configurations in whichproperties of imaginary components of the output impedances are the sameare therefore able to be used.

To be more specific, the matching region and the output impedances of atleast two filters are able to be made close to each other by adjustingat least two of the impedances (Z (LNAin+ADJ_A), Z (LNAin+ADJ_B), and Z(LNAin+ADJ_C)) of the respective paths 10 a to 10 c when the low noiseamplifier 40 is seen from the respective filters 10A to 10C to beinductive. In addition, the NF matching impedance and the gain matchingimpedance are able to be made close to each other. To be specific, theNF matching impedances (“NF_min_A” and “NF_min_B” in the FIG. 3C) andthe impedances (“Gain_max_A” and “Gain_max_B” in FIG. 3C) at which thegain is maximum are able to be made close to each other as illustratedin FIG. 3C by adjusting the impedances (Z (LNAin+ADJ_A) and Z(LNAin+ADJ_B)) to be inductive as illustrated in FIG. 3B. This iscapable of further increasing the gain while further suppressing thedeterioration in the NF.

Moreover, with the high-frequency module 1 in the present preferredembodiment, by configuring the connection circuit (switch 20 in thepresent preferred embodiment) by the switch element, when any one of theplurality of selection terminals is connected to the common terminal,the plurality of paths in which the plurality of filters 10A to 10C areprovided are not connected to one another. Therefore, this configurationis able to enhance isolation among the plurality of filters 10A to 10C.

The common terminal of the switch 20 may be connected to two or moreselection terminals of the plurality of selection terminals.

Furthermore, with the high-frequency module 1 in the present preferredembodiment, the plurality of filters 10A to 10C include the elastic waveresonators and are thus reduced in size, thus further reducing thehigh-frequency module 1 in size. The plurality of filters 10A to 10Cinclude the elastic wave resonators having generally high Qcharacteristics, thus reducing losses of the plurality of filters 10A to10C. Accordingly, the gain is increased while suppressing thedeterioration in the NF for the overall high-frequency module.

First Variation

In the above-described preferred embodiment, the switch 20 has beendescribed as an example of the connection circuit that commonly connectsthe plurality of paths 10 a to 10 c. The connection circuit is nothowever limited to have this configuration and may be configured by amultiplexer, for example. As a high-frequency module according to afirst variation of the present preferred embodiment, such ahigh-frequency module is described. In this variation and each ofsubsequent variations, description of the same configurations as thosein the above-described preferred embodiment is omitted.

FIG. 5 is a circuit configuration diagram of a high-frequency module 101in the first variation of the preferred embodiment.

The high-frequency module 101 illustrated in FIG. 5 is different fromthe high-frequency module 1 illustrated in FIG. 1 in the point that itincludes a multiplexer 120 instead of the switch 20.

The multiplexer 120 includes a first terminal connected to the low noiseamplifier 40 and a plurality of second terminals connected to theplurality of filters 10A to 10C in an individual correspondence manner.To be specific, the multiplexer 120 is a connection circuit including aplurality of individual terminals connected to the plurality of filters10A to 10C in the individual correspondence manner and a common terminalconnected to the low noise amplifier 40. Specifically, the multiplexer120 includes a plurality of filters that are individually connected to aplurality of paths connecting the plurality of individual terminals andthe common terminal. In the variation, the multiplexer 120 includes alow pass filter connected to the path connecting the individual terminal(one of the plurality of second terminals) connected to the path 10 aand the common terminal (first terminal) and covering Band A in its passband, a band pass filter connected to the path connecting the individualterminal (another one of the plurality of second terminals) connected tothe path 10 b and the common terminal (first terminal) and covering BandB in its pass band, and a high pass filter connected to the pathconnecting the individual terminal (still another one of the pluralityof second terminals) connected to the path 10 c and the common terminal(first terminal) and covering Band C in its pass band. The configurationof the multiplexer 120 is not limited thereto and may be configured by aplurality of band pass filters, for example. It should be noted that thenumber of common terminals (first terminals) is not limited to one and aplurality of common terminals may be provided.

Even with the above-described configuration, the high-frequency module101 that is capable of increasing a gain while suppressing deteriorationin an NF, is reduced in size, and is compatible with multiple bands isable to be provided in the same manner as the first preferredembodiment.

Furthermore, with the high-frequency module 101 in the variation, two ormore high-frequency signals after passing through two or more filtersamong the plurality of filters are able to be transmitted simultaneouslyby configuring the connection circuit by the multiplexer 120. Therefore,the high-frequency module is able to be applied to CA (carrieraggregation) in which transmission and reception are performed using twoor more bands of the plurality of bands simultaneously.

In general, insertion loss of the multiplexer is lower than that of theswitch. With this variation, the gain is therefore able to be furtherincreased while further suppressing the deterioration in the NF for theoverall high-frequency module 101 in comparison with the configurationin which the switch is provided as the connection circuit.

Second Variation

In the above-described preferred embodiment and the first variationthereon, one circuit element (switch 20 in the above-described preferredembodiment and multiplexer 120 in the first variation of theabove-described preferred embodiment) has been described as the exampleof the connection circuit that commonly connects the plurality of paths10 a to 10 c. The connection circuit is not however limited to have thisconfiguration and may be configured by connecting a plurality of circuitelements in a multistage arrangement. As a high-frequency moduleaccording to a second variation of the above-described preferredembodiment, such high-frequency modules are described.

FIG. 6A is a circuit configuration diagram of a high-frequency module201A according to a first example of the second variation of theabove-described preferred embodiment. FIG. 6B is a circuit configurationdiagram of a high-frequency module 201B according to a second example ofthe second variation of the above-described preferred embodiment. FIG.6C is a circuit configuration diagram of a high-frequency module 201Caccording to a third example of the second variation of theabove-described preferred embodiment.

As illustrated in FIG. 6A to FIG. 6C, all of the high-frequency modules201A to 201C in the first to third examples of the variation includefour filters 10A to 10D. The filters 10A to 10D have pass bands whichare different from one another and Band D is assigned to the pass bandof the filter 10D.

The high-frequency module 201A illustrated in FIG. 6A includes aconnection circuit 220A including switches 221SW, 222SW, and 223SW.

The switch 221SW is a first initial stage connection circuit thatcommonly connects some paths (paths 10 a and 10 b in this example) amonga plurality of paths 10 a to 10 d. That is to say, the switch 221SWcommonly connects a portion of the plurality of paths 10 a to 10 d.

The switch 222SW is a second initial stage connection circuit thatcommonly connects at least two paths (paths 10 c and 10 d in thisexample), which are different from the above-described some paths, amongthe plurality of paths 10 a to 10 d. That is to say, the switch 222SWcommonly connects at least another portion of the plurality of paths 10a to 10 d.

The switch 223SW is a posterior stage connection circuit that isconnected in a multistage arrangement to the first initial stageconnection circuit (switch 221SW in this example) and the second initialstage connection circuit (switch 222SW in this example). The switch223SW commonly connects a path 220 a connected to a common terminal ofthe first initial stage connection circuit and a path 220 b connected toa common terminal of the second initial stage connection circuit.

In the variation, each of the switches 221SW, 222SW, and 223SW is anSPDT (Single Pole Double Throw)-type switch element and a selectionterminal thereof that is connected to the common terminal is switchedwith a control signal from a controller (not illustrated).

The high-frequency module 201B illustrated in FIG. 6B is different fromthe high-frequency module 201A illustrated in FIG. 6A in the point thatit includes a connection circuit 220B including a diplexer 223DP insteadof the switch 223SW.

The diplexer 223DP is a posterior stage connection circuit similar tothe switch 223SW and includes a first terminal connected to the lownoise amplifier 40 and a plurality of second terminals connected to thefirst initial stage connection circuit (switch 221SW in this example)and the second initial stage connection circuit (switch 222SW in thisexample) in an individual correspondence manner. To be specific, thediplexer 223DP includes a low pass filter covering Band A and Band B inits pass band and a high pass filter covering Band C and Band D in itspass band. The low pass filter is connected to a path connecting theindividual terminal (one of the plurality of second terminals) connectedto the path 220 a and the common terminal (first terminal). The highpass filter is connected to a path connecting the individual terminal(the other one of the plurality of second terminals) connected to thepath 220 b and the common terminal (first terminal).

The high-frequency module 201C illustrated in FIG. 6C is different fromthe high-frequency module 201A illustrated in FIG. 6A in the point thatit includes a connection circuit 220C including diplexers 221DP and222DP instead of the switches 221SW and 222SW.

The diplexer 221DP is a first initial stage connection circuit similarto the switch 221SW and includes a first terminal connected to theposterior stage connection circuit (switch 223SW in this example) and aplurality of second terminals connected to the filters 10A and 10B in anindividual correspondence manner. To be specific, the diplexer 221DPincludes a low pass filter covering Band A in its pass band and a highpass filter covering Band B in its pass band. The low pass filter isconnected to a path connecting the individual terminal (one of theplurality of second terminals) connected to the path 10 a and the commonterminal (first terminal). The high pass filter is connected to a pathconnecting the individual terminal (the other one of the plurality ofsecond terminals) connected to the path 10 b and the common terminal(first terminal).

The diplexer 222DP is a second initial stage connection circuit similarto the switch 222SW and includes a first terminal connected to theposterior stage connection circuit (switch 223SW in this example) and aplurality of second terminals connected to the filters 10C and 10D in anindividual correspondence manner. To be specific, the diplexer 222DPincludes a low pass filter covering Band C in its pass band and a highpass filter covering Band D in its pass band. The low pass filter isconnected to a path connecting the individual terminal (one of theplurality of second terminals) connected to the path 10 c and the commonterminal (first terminal). The high pass filter is connected to a pathconnecting the individual terminal (the other one of the plurality ofsecond terminals) connected to the path 10 d and the common terminal(first terminal).

Even with the above-described configurations, the high-frequency modules201A to 201C that are capable of increasing a gain while suppressingdeterioration in an NF, are reduced in size, and are compatible withmultiple bands are able to be provided in the same manner as the firstpreferred embodiment.

Each of the high-frequency modules 201A to 201C in the variation has theconfiguration of the connection circuit in which the circuits (first andsecond initial stage connection circuits and posterior stage connectioncircuit) are connected in a multistage arrangement, thus enhancingisolation among the plurality of filters.

Third Variation

In the above-described preferred embodiment and the first and secondvariations thereon, all of the paths in which the plurality of filtersare provided connect the respective filters and the connection circuitwithout connecting impedance elements. Alternatively, there may be apath that connects the filter and the connection circuit with theimpedance element connected therebetween. As a high-frequency moduleaccording to a third variation of the above-described preferredembodiment, such a high-frequency module is described.

Although in the variation, two filters to which Band A or Band B isassigned to their pass bands are described as examples of the first andsecond filters and a filter to which Band C is assigned to its pass bandis described as an example of the third filter, a correspondencerelationship between the first to third filters and these filters is notlimited thereto.

FIG. 7 is a circuit configuration diagram of a high-frequency module 301in the third variation of the above-described preferred embodiment.

The high-frequency module 301 illustrated in FIG. 7 is different fromthe high-frequency module 1 illustrated in FIG. 1 in the point that itincludes a filter 310C instead of the filter 10C and an impedanceadjustment circuit 330 connected between the filter 310C and the switch20.

The pass band of the filter 310C is largely different from those of thefilters 10A and 10B (for example, by equal to or larger than the bandwidth of the pass band). For example, the pass band of the filter 310Cis in an LB band and the pass bands of the filters 10A and 10B are in anMB band. For example, the output impedance (in-band output impedance) ofthe filter 310C in its respective pass band is largely different fromthe output impedances (out-of-band impedances) thereof in the pass bandsof the filters 10A and 10B.

The impedance adjustment circuit 330 is a functional circuit that isconnected between the third filter (filter 310C in the variation) amongthe plurality of filters 10A, 10B, and 310C and the switch 20 and isconfigured or programmed to perform a predetermined function (functionof adjusting the impedance in this example). The impedance adjustmentcircuit 330 is a second impedance adjustment circuit that generates asecond impedance when a circuit portion in which the impedanceadjustment circuit 330 is connected to the third filter is seen from theinput side of the low noise amplifier 40 close to a matching region inthe pass band of the third filter on the Smith chart. The circuitconfiguration of the impedance adjustment circuit 330 and a constant ofan impedance element are not particularly limited and it is sufficientthat the circuit configuration and the constant are set to cause thesecond impedance to be located in the above-described matching region.

Even with the above-described configuration, the high-frequency module301 that is capable of increasing a gain while suppressing deteriorationin an NF, is reduced in size, and is compatible with multiple bands isable to be provided in the same manner as the first preferredembodiment.

As described in the above-described preferred embodiment, the impedanceadjustment circuit 30 adjusts the position of the matching region thatincreases the gain while suppressing the deterioration in the NF on theSmith chart. The impedance adjustment circuit 30 cannot enlarge thematching region although it can adjust the position of the matchingregion. Therefore, when the frequencies of the plurality of bands (BandA to Band C in this variation) are separated from one another, theeffect of increasing the gain while suppressing the deterioration in theNF is difficult to be exerted in, in particular, the band (Band C inthis variation) the frequency of which is separated from those of theother bands in some cases. As a combination of Band A to Band C, acombination of Bands 12, 13, and 7 of 3GPP (Third Generation PartnershipProject) that is used in LTE (Long Term Evolution) is exemplified.

To cope with this problem, the high-frequency module 301 in thevariation includes the impedance adjustment circuit (second impedanceadjustment circuit) and is thus able to significantly improve oroptimize balance between NF performance and gain performance for each ofthe first to third filters even when the frequency intervals of the passband of the third filter (filter 310 in the variation) and the passbands of the first and second filters (filters 10A and 10B in thevariation) are largely separated from each other. Therefore, theplurality of bands with which the high-frequency module is compatible isable to be further widened.

Fourth Variation

The configuration in the second variation of the above-describedpreferred embodiment and the configuration of the third variation of theabove-described preferred embodiment may be combined. That is to say,the connection circuit may include an impedance adjustment circuitconnected between the first initial stage connection circuit and theposterior stage connection circuit. As a high-frequency module accordingto a fourth variation of the above-described preferred embodiment, sucha high-frequency module is described.

FIG. 8 is a circuit configuration diagram of a high-frequency module 401in the fourth variation of the above-described preferred embodiment.

The high-frequency module 401 illustrated in FIG. 8 is different fromthe high-frequency module 201A illustrated in FIG. 6A in the point thatit includes filters 410A and 410B instead of the filters 10A and 10B andfurther includes an impedance adjustment circuit 430.

The filters 410A and 410B have output impedances Z (Fout_A) and Z(Fout_B) located in different regions from a matching region in theirrespective pass bands on the Smith chart.

The impedance adjustment circuit 430 is a third impedance adjustmentcircuit that is connected between the first initial stage connectioncircuit (switch 221SW in the variation) and the posterior stageconnection circuit (switch 223SW in the variation). The impedanceadjustment circuit 430 generates a third impedance when a circuitportion in which the impedance adjustment circuit 430 is connected tothe first initial stage connection circuit is seen from the input sideof the low noise amplifier 40 close to the above-described matchingregion in the pass bands of some filters (filters 410A and 410B in thevariation) provided in some paths (paths that are commonly connected bythe first impedance adjustment circuit) among the plurality of filters410A, 410B, 10C, and 10D on the Smith chart. The circuit configurationof the impedance adjustment circuit 430 and a constant of an impedanceelement are not particularly limited and it is sufficient that thecircuit configuration and the constant are set to cause the thirdimpedance to be located in the above-described matching region.

Even with the above-described configuration, the high-frequency module401 that is capable of increasing a gain while suppressing deteriorationin an NF, is reduced in size, and is compatible with multiple bands isable to be provided in the same manner as the first preferredembodiment.

With the high-frequency module 401 in the variation, the connectioncircuit 420 includes the impedance adjustment circuit 430 (thirdimpedance adjustment circuit), thus providing the following effects.

The frequency bands of the bands assigned to the some filters (filters410A and 410B in the variation) provided in the some paths which arecommonly connected by the switch 221SW (first initial stage connectioncircuit) among the plurality of bands with which the high-frequencymodule 401 is compatible are referred to as a first frequency band. Thefrequency bands of the bands assigned to at least two filters (filters10C and 10D in the variation) provided in at least two paths which arecommonly connected by the switch 222SW (second initial stage connectioncircuit) among the plurality of bands with which the high-frequencymodule 401 is compatible are referred to as a second frequency band.

By including the impedance adjustment circuit 430 as described above,balance between NF performance and gain performance are able to besignificantly improved or optimized for each of the above-described somefilters and the above-described at least two filters even when thefrequency intervals of the first frequency band and the second frequencyband are largely separated from each other. Therefore, thehigh-frequency module 401 is able to be compatible with a large numberof bands having largely different frequencies in the plurality of bandswith which the high-frequency module 401 is compatible. The bands havingthe largely different frequencies indicate bands the frequencies ofwhich are largely different, such as an HB band (for example, band ofabout 2.5 GHz) and an MB band (for example, band of about 1800 MHz).

In the variation, the filters 410A and 410B have been described as theexamples of the filters that are connected to the impedance adjustmentcircuit 430. The filters that are connected to the impedance adjustmentcircuit 430 are not however limited to the above-described example andmay be, for example, the filters 10C and 10D. That is to say, theimpedance adjustment circuit 430 may be connected between the switch222SW and the switch 223SW. In this case, the switch 222SW correspondsto the first initial stage connection circuit and the switch 221SWcorresponds to the second initial stage connection circuit.

Fifth Variation

In the above-described preferred embodiment and the first to fourthvariations thereon, the connection circuit (or the first and secondinitial stage connection circuits and the posterior stage connectioncircuit configuring the connection circuit) connects the plurality ofpaths with the circuit elements such as the switches (the multiplexersor the diplexers). The connection circuit is not however limited to thecircuit element and may be a connection point that commonly connects theplurality of paths (wirings). In this case, one impedance adjustmentcircuit may include an impedance adjustment circuit connected at aprevious stage (filter side) of the connection point and an impedanceadjustment circuit connected at a subsequent stage (LNA side) thereof.As a high-frequency module according to a fifth variation of the presentpreferred embodiment, such a high-frequency module is described.

FIG. 9 is a circuit configuration diagram of a high-frequency module 501in the fifth variation of the present preferred embodiment.

The high-frequency module 501 illustrated in FIG. 9 is different fromthe high-frequency module 401 illustrated in FIG. 8 in the point that itincludes filters 10A and 10B instead of the filters 410A and 410B andfilters 510C and 510D instead of the filters 10C and 10D. Furthermore, aconnection circuit 520 of the high-frequency module 501 is differentfrom the connection circuit 420 of the high-frequency module 401 in thepoints that the posterior stage connection circuit includes a branchpoint N (branch portion) and an impedance adjustment circuit 532 (thirdimpedance adjustment circuit) is provided in a path connecting theposterior stage connection circuit and the switch 222SW.

The pass bands of the filters 510C and 510D are largely different fromthose of the filters 10A and 10B (for example, by equal to or largerthan the band width of the pass band). For example, the pass bands ofthe filters 510C and 510D are in an LB band and the pass bands of thefilters 10A and 10B are in an MB band. For example, the outputimpedances (in-band output impedances) of the respective filters 510Cand 510D in their respective pass bands are largely different from theoutput impedances (out-of-band impedances) thereof in the pass bands ofthe filters 10A and 10B.

The impedance adjustment circuit 532 is a third impedance adjustmentcircuit that is connected between the first initial stage connectioncircuit (switch 222SW in the variation) and the posterior stageconnection circuit (branch point N in the variation). The impedanceadjustment circuit 532 adjusts a third impedance when a circuit portionin which the impedance adjustment circuit 532 is connected to the firstinitial stage connection circuit is seen from the input side of the lownoise amplifier 40 to be located in the above-described matching regionin the pass bands of the filters (filters 510C and 510D in thevariation) connected to the first initial stage connection circuit onthe Smith chart.

That is to say, the impedance adjustment circuit 532 provides oneimpedance adjustment circuit 530 together with the impedance adjustmentcircuit 30. In other words, as for the impedance adjustment circuit 530,when the point at the low noise amplifier 40 side is assumed to be astart point, the switch 222SW is connected to an end point and theswitch 221SW is connected to the branch point N between the start pointand the end point. Therefore, the one impedance adjustment circuit 530including these two impedance adjustment circuits performs two functionsof moving the matching region for the filters 10A and 10B and moving thematching region for the filters 510C and 510D.

Even with the above-described configuration, the high-frequency module501 that is capable of increasing a gain while suppressing deteriorationin an NF, is reduced in size, and is compatible with multiple bands isable to be provided in the same manner as the first preferredembodiment.

The high-frequency module 501 in the variation is able to have thesimplified configuration by providing the posterior stage connectioncircuit with the branch point N (branch portion). Moreover, thisconfiguration enables the high-frequency module to be applied to carrieraggregation in which transmission and reception are performed using twoor more bands of the plurality of bands simultaneously.

Sixth Variation

In the above-described preferred embodiment and the first to fifthvariations thereon, the high-frequency module preferably includes oneimpedance adjustment circuit 30 (first impedance adjustment circuit) andone low noise amplifier 40. It should be noted that the numbers of themare not limited to one and a plurality of them may be provided. As ahigh-frequency module according to a sixth variation of theabove-described preferred embodiment, such a high-frequency module isdescribed.

FIG. 10 is a circuit configuration diagram of a high-frequency module601 in the sixth variation of the above-described preferred embodiment.

The high-frequency module 601 illustrated in FIG. 10 is different fromthe high-frequency module 1 illustrated in FIG. 1 in the point that itincludes two impedance adjustment circuits 30A and 30B and two low noiseamplifiers 40A and 40B instead of the impedance adjustment circuit 30and the low noise amplifier 40. Furthermore, the high-frequency module601 includes a DPnT (Double Pole n Throw)-type (n is the number offilters and four in the variation) switch 620 instead of the SPnT-typeswitch 20. A selection terminal of the switch 620, which is connected toeach common terminal, is switched with a control signal from acontroller (not illustrated).

With this configuration, for example, the low noise amplifier 40A isable to amplify a high-frequency signal (high-frequency receptionsignal) of an HB band and the low noise amplifier 40B is able to amplifya high-frequency signal (high-frequency reception signal) of an LB band.Accordingly, the appropriate low noise amplifier is able to be used foreach of the HB band and the LB band, thus increasing a gain whilesuppressing deterioration in an NF and further widening the plurality ofbands with which the high-frequency module 601 is compatible.

This configuration enables the high-frequency module to be applied tocarrier aggregation in which transmission and reception are performedusing two or more bands of the plurality of bands simultaneously.

In the variation, the numbers of impedance adjustment circuits and lownoise amplifiers are not limited to the above-mentioned numbers and maybe three or more. With this configuration, the switch 620 is not limitedto be of the DPnT type and the same number of common terminals as thoseof impedance adjustment circuits and low noise amplifiers may beprovided.

Seventh Variation

Although in the first example of the second variation of theabove-described preferred embodiment, the switch 221SW and the switch222SW include the individual switch elements, they may be configured byone switch element. That is to say, one initial stage connection circuitand one posterior stage connection circuit may be provided. As ahigh-frequency module according to a seventh variation of theabove-described preferred embodiment, such a high-frequency module isdescribed.

FIG. 11 is a circuit configuration diagram of a high-frequency module701 in the seventh variation of the above-described preferredembodiment.

The high-frequency module 701 illustrated in FIG. 11 is different fromthe high-frequency module 201A illustrated in FIG. 6A in the point thatit includes a connection circuit 720 including a switch 721 and a switch723 instead of the connection circuit 220A including the switches 221SWand 222SW and the switch 223SW. It should be noted that the switch 723has the same configuration as that of the switch 223SW and descriptionthereof is therefore omitted below.

The switch 721 is a switch in which the switch 221SW (first initialstage connection circuit) and the switch 222SW (second initial stageconnection circuit) are integrated and is a DPnT-type (n is the numberof filters and four in the variation) switch in the variation. Aselection terminal of the switch 721, which is connected to each commonterminal, is switched with a control signal from a controller (notillustrated), in the same manner as the switch 620.

Even with this configuration, the same effects as those provided in thefirst example of the second variation of the above-described preferredembodiment are able to be provided.

It should be noted that the switch 723 is not limited to be of the SPDTtype and may three or more selection terminals. With this configuration,the switch 721 is not limited to be of the DPnT type and may include thesame number of common terminals as that of the selection terminals ofthe switch 723.

Eighth Variation

In the above-described preferred embodiment and the first to seventhvariations thereon, the high-frequency module includes any circuitelement as the connection circuit. The connection circuit may howeverinclude no circuit element and be configured by commonly connecting aplurality of paths. As a high-frequency module according to an eighthvariation of the above-described preferred embodiment, such ahigh-frequency module is described.

FIG. 12 is a circuit configuration diagram of a high-frequency module801 in the eighth variation of the above-described preferred embodiment.

The high-frequency module 801 illustrated in FIG. 12 is different fromthe high-frequency module 1 illustrated in FIG. 1 in the point that theplurality of paths 10 a to 10 c are commonly connected at a commonconnection point 820 instead of the switch (connection circuit). That isto say, the common connection point 820 corresponds to a connectioncircuit in the variation.

This configuration reduces the connection circuit in size, thus furtherreducing the overall high-frequency module 801 in size.

Furthermore, this configuration enables the high-frequency module to beapplied to CA (Carrier Aggregation) in which transmission and receptionare performed using a plurality of bands simultaneously.

Ninth Variation

The configuration that is applied to CA is not limited to theabove-described configuration and, for example, the configurationincluding a switch capable of connecting a common terminal to aplurality of individual terminals simultaneously may be provided. FIG.13A is a circuit configuration diagram of a high-frequency module 901Aaccording to a first example of the ninth variation of theabove-described preferred embodiment. FIG. 13B is a circuitconfiguration diagram of a high-frequency module 901B according to asecond example of the ninth variation of the above-described preferredembodiment. FIG. 13C is a circuit configuration diagram of ahigh-frequency module 901C according to a third example of the ninthvariation of the above-described preferred embodiment.

The high-frequency module 901A illustrated in FIG. 13A is different fromthe high-frequency module 201A illustrated in FIG. 6A in the point thatit includes a connection circuit 920A including a switch 923SW insteadof the switch 223SW.

The switch 923SW is a switch capable of connecting a common terminalconnected to the impedance adjustment circuit 30 to two individualterminals that are respectively connected to the two paths 220 a and 220b simultaneously. Selection terminals of the switch 923W, which areconnected to the common terminal, and the number thereof are switchedwith a control signal from a controller (not illustrated).

The high-frequency module 901A configured as described above is able tobe compatible with CA with any one of Band A and Band B and any one ofBand C and Band D by connecting the common terminal of the switch 923SWto the two individual terminals thereof simultaneously.

The high-frequency module 901B illustrated in FIG. 13B is different fromthe high-frequency module 201B illustrated in FIG. 6B in the point thatit includes a connection circuit 920B including switches 921SW and 922SWinstead of the switches 221SW and 222SW.

The switch 921SW is a switch capable of connecting a common terminalconnected to the diplexer 223DP as the posterior stage connectioncircuit to two individual terminals that are respectively connected tothe two paths 10 a and 10 b simultaneously. The switch 922SW is a switchcapable of connecting a common terminal connected to the diplexer 223DPas the posterior stage connection circuit to two individual terminalsthat are respectively connected to the two paths 10 c and 10 dsimultaneously. The switches 921SW and 922SW preferably are SPDT-typeswitches and selection terminals thereof, which are connected to thecommon terminals, and the numbers thereof are switched with a controlsignal from a controller (not illustrated).

The high-frequency module 901B configured as described above is able tobe compatible with CA with two or more bands of Band A to Band D with atleast one of the switches 921SW and 922SW.

The high-frequency module 901C illustrated in FIG. 13C is different fromthe high-frequency module 201C illustrated in FIG. 6C in the point thatit includes a connection circuit 920C including the above-describedswitch 923SW instead of the switch 223SW.

The high-frequency module 901C configured as described above is able tobe compatible with CA with two or more bands of Band A to Band D byconnecting the common terminal of the switch 923SW to the two individualterminals thereof simultaneously.

Tenth Variation

The switch connecting the common terminal to the plurality of selectionterminals simultaneously, which has been described in the ninthvariation, may be used to adjust an impedance. As a high-frequencymodule according to a tenth variation of the above-described preferredembodiment, a high-frequency module including the above-described switchis described.

FIG. 14 is a circuit configuration diagram of a high-frequency module1001 in the tenth variation of the above-described preferred embodiment.

The high-frequency module 1001 illustrated in FIG. 14 is different fromthe high-frequency module 301 illustrated in FIG. 7 in the point that itincludes a switch 1020 instead of the switch and further includes anaddition circuit 630 to adjust an impedance.

The switch 1020 is a switch including one common terminal and fourindividual terminals and capable of connecting the common terminal totwo or more individual terminals among the four individual terminalssimultaneously. Selection terminals of the switch 1020, which areconnected to the common terminal, and the number thereof are switchedwith a control signal from a controller (not illustrated).

The addition circuit 630 is a circuit that is connected between oneindividual terminal of the switch 1020 and the ground and is configuredor programmed to perform a predetermined function. That is to say, theaddition circuit 630 plays the predetermined function by being connectedbetween a main path that transmits a high-frequency signal and theground when the common terminal of the switch 1020 is simultaneouslyconnected to the individual terminal connected to the addition circuit630 and another individual terminal.

The addition circuit 630 is, for example, an impedance element such asan inductor and a capacitor that is connected between the individualterminal of the switch 1020 and the ground. With the addition circuit630 configured as described above, the impedance element adjusts theimpedance of the main path by being connected between the main path andthe ground when the common terminal of the switch 1020 is simultaneouslyconnected in the above-described manner.

Furthermore, the addition circuit 630 is, for example, a resonancecircuit such as an LC parallel resonance circuit, an LC series resonancecircuit, or a distributed constant-type resonator, which is connectedbetween the individual terminal of the switch and the ground. With theaddition circuit 630 configured as described above, the resonancecircuit generates a pole by being connected between the main path andthe ground when the common terminal of the switch 1020 is simultaneouslyconnected in the above-described manner. To be specific, the resonancecircuit generates an attenuation pole at a frequency at which theimpedance is minimum (0 ideally) and generates a pass band at afrequency at which the impedance is maximum (infinite ideally).

As described above, the high-frequency module 1001 in the variationswitches presence or absence of the predetermined function that theaddition circuit 630 plays by switching whether the common terminal ofthe switch 1020 is connected to the individual terminal to which theaddition circuit 630 is connected while being connected to at leastanother individual terminal.

Eleventh Variation

The impedance adjustment circuit as described above may have theconfiguration capable of varying an impedance. As a high-frequencymodule according to an eleventh variation of the above-describedpreferred embodiment, a high-frequency module including theabove-described impedance adjustment circuit is described.

FIG. 15 is a circuit configuration diagram of a high-frequency module1101 in the eleventh variation of the above-described preferredembodiment.

The high-frequency module 1101 illustrated in FIG. 15 is different fromthe high-frequency module 301 illustrated in FIG. 7 in the point that itincludes an impedance adjustment circuit 1030 capable of varying animpedance instead of the impedance adjustment circuit 30.

FIGS. 16A to 16D show examples of the impedance adjustment circuit 1030according to the variation.

As illustrated in FIG. 16A, the impedance adjustment circuit 1030 may beconfigured by, for example, connecting in parallel a plurality of seriescircuits each of which includes an inductor La and a pair of switchesSWa connected in series to both ends thereof. With this configuration,the inductors La connected in parallel are able to be switched byswitching ON and OFF of each of the pairs of switches SWa, thus varyingthe inductance of the overall impedance adjustment circuit 1030.

As illustrated in FIG. 16B, the impedance adjustment circuit 1030 may beprovided by, for example, connecting in parallel a plurality of seriescircuits each of which includes a capacitor Cb and a pair of switchesSWb connected in series to both ends thereof. With this configuration,the capacitors Cb connected in parallel are able to be switched byswitching ON and OFF of each of the pairs of switches SWb, thus varyingthe capacitance of the overall impedance adjustment circuit 1030.

In the configurations illustrated in FIG. 16A and FIG. 16B, it issufficient that the plurality of series circuits connected in parallelmaybe provided, and two or four or more series circuits may be provided.Furthermore, one of the pair of switches may not be provided.

As illustrated in FIG. 16C, the impedance adjustment circuit 1030 may beprovided by, for example, connecting in series a plurality of parallelcircuits each of which includes an inductor Lc and a switch SWcconnected thereto in parallel. With this configuration, the inductors Lcconnected in series are able to be switched by individually switching ONand OFF of the plurality of switches SWc, thus varying the inductance ofthe overall impedance adjustment circuit 1030.

In the configuration illustrated in FIG. 16C, capacitors may be providedinstead of the inductors Lc.

Alternatively, as illustrated in FIG. 16D, the impedance adjustmentcircuit 1030 may include, for example, a short stub Sd provided at anode A on a main path to transmit a high-frequency signal and aplurality of switches SWd. The plurality of switches SWd are connectedbetween a plurality of nodes with different distances from the node A onthe short stub Sd and the ground. With this configuration, the node thatis connected to the ground on the short stub Sd is able to be switchedby switching the switch SWd which is turned ON, thus varying theimpedance of the overall impedance adjustment circuit 1030.

Other Variations

Although high-frequency modules according to preferred embodiments ofthe present invention and variations and modifications thereto have beendescribed above, the present invention is not limited by theabove-described preferred embodiment and variations and modifications.The present invention also encompasses other preferred embodiments thatare implemented by combining desired components, elements, features,characteristics, functions, etc., in the above-described preferredembodiment and variations and modifications, and variations andmodifications obtained by adding various changes to the above-describedpreferred embodiments, which are conceived by those skilled in the art,without departing from the gist of the present invention, and variousapparatuses incorporating high-frequency modules according to preferredembodiments of the present invention and variations and modificationsthereto.

For example, a preferred embodiment of the present invention alsoencompasses the communication apparatus 4 including the high-frequencymodule 1 described in the first preferred embodiment and the RFIC 3 (RFsignal processing circuit). The communication apparatus 4 enables acommunication apparatus that is capable of increasing a gain whilesuppressing deterioration in an NF, is reduced in size and is compatiblewith multiple bands.

In the above description, for example, the high-frequency moduleincludes the first impedance adjustment circuit that is connectedbetween the connection circuit and the low noise amplifier 40. However,the high-frequency module may not include the first impedance adjustmentcircuit. That is to say, even when impedance adjustment is not made bythe first impedance adjustment circuit, it is sufficient that each ofthe first and second filters has the output impedance located in thematching region between the NF matching impedance and the gain matchingimpedance.

In the above description, each of the filters preferably has the outputimpedance with the capacitive property in its respective pass band.However, each of the filters may have the output impedance having aninductive property in its respective pass band or the output impedancehaving no imaginary component. Alternatively, some filters may have theoutput impedances with the capacitive properties in their respectivepass bands whereas other filters may have the output impedances havingthe inductive properties in their respective pass bands.

The respective filters may include elements that are different from theelastic wave resonators and may be configured by, for example, LCelements.

In the third variation of the above-described preferred embodiment, theimpedance adjustment circuit 330 has been described as the example ofthe functional circuit. The functional circuit is not however limited tohave the configuration and may be, for example, a filter such as a lowpass filter, a coupler, or an isolator. The function that is performedby the functional circuit is able to influence only a specific band(Band C in this example) passing through the third filter by includingthe functional circuit. When, for example, the low pass filter isprovided as the functional circuit, attenuation characteristics at thehigh frequency side are able to be enhanced by an action of the low passfilter for the above-described specific band.

The above-described functional circuit may be provided instead of theimpedance adjustment circuit 430 in the fourth variation of theabove-described preferred embodiment. The function that is exerted bythe functional circuit is able to influence only specific bands (Band Aand Band B in this example) passing through the filters (filters 410Aand 410B) provided in the paths (paths 10 a and 10 b) that are commonlyconnected by the first initial stage connection circuit.

Preferred embodiments of the present invention are able to be widelyused for communication apparatuses such as a cellular phone as ahigh-frequency module and a communication apparatus, which can beapplied to a multiband system, having preferable balance between NFperformance and gain performance, and being reduced in size.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A high-frequency module comprising: a pluralityof filters including first and second filters and including pass bandswhich are different from one another; a connection circuit that commonlyconnects a plurality of paths in which the plurality of filters arerespectively provided; and a low noise amplifier that is connected tothe connection circuit; wherein in paths in which the first and secondfilters are respectively provided among the plurality of paths, therespective filters and the connection circuit are connected withoutconnecting impedance elements; each of the first and second filters hasan output impedance located in a matching region between a noise figurematching impedance at which a noise figure of the low noise amplifier isminimum and a gain matching impedance at which a gain of the low noiseamplifier is maximum in a pass band of each of the first and secondfilters on a Smith chart.
 2. The high-frequency module according toclaim 1, further comprising a first impedance adjustment circuit that isconnected between the connection circuit and the low noise amplifier,wherein the first impedance adjustment circuit adjusts a first impedancewhen a circuit portion in which the first impedance adjustment circuitis connected to the low noise amplifier is seen from output sides of theplurality of filters in a case in which the noise figure is minimum andthe gain is maximum.
 3. The high-frequency module according to claim 2,wherein the first impedance adjustment circuit adjusts the firstimpedance to be any one of inductive or capacitive in both of the passbands of the first filter and the second filter among the plurality offilters in the case in which the noise figure is minimum and the gain ismaximum.
 4. The high-frequency module according to claim 3, wherein eachof the first and second filters has the output impedance with acapacitive property in the respective pass band of each of the first andsecond filters; and the first impedance adjustment circuit adjusts thefirst impedance to be inductive in both of the pass bands of the firstfilter and the second filter among the plurality of filters in the casein which the noise figure is minimum and the gain is maximum.
 5. Thehigh-frequency module according to claim 1, further comprising afunctional circuit that is connected between a third filter of theplurality of filters and the connection circuit and is configured orprogrammed to perform a predetermined function.
 6. The high-frequencymodule according to claim 5, wherein the functional circuit is a secondimpedance adjustment circuit that generates a second impedance when acircuit portion in which the functional circuit is connected to thethird filter is seen from an input side of the low noise amplifier closeto the matching region in a pass band of the third filter on the Smithchart.
 7. The high-frequency module according to claim 1, whereinwherein the plurality of filters include three or more filters; and eachof the filters and the connection circuit are connected withoutconnecting an impedance element in each of the plurality of paths. 8.The high-frequency module according to claim 1, wherein the connectioncircuit includes a switch including a plurality of selection terminalsconnected to the plurality of filters in an individual correspondencemanner and a common terminal connected to the low noise amplifier. 9.The high-frequency module according to claim 1, wherein the connectioncircuit is a multiplexer including a first terminal connected to the lownoise amplifier and a plurality of second terminals connected to theplurality of filters in an individual correspondence manner.
 10. Thehigh-frequency module according to claim 1, wherein the plurality offilters include four or more filters; and the connection circuitincludes: a first initial stage connection circuit that commonlyconnects some paths among the plurality of paths; a second initial stageconnection circuit that commonly connects at least two paths which aredifferent from the some paths among the plurality of paths; and aposterior stage connection circuit that is connected in a multistagearrangement to the first and second initial stage connection circuits.11. The high-frequency module according to claim 10, wherein theconnection circuit further includes a third impedance adjustment circuitthat is connected between the first initial stage connection circuit andthe posterior stage connection circuit and generates a third impedancewhen a circuit portion in which the third impedance adjustment circuitis connected to the first initial stage connection circuit is seen froman input side of the low noise amplifier close to the matching region inpass bands of some filters provided in the some paths among theplurality of filters on the Smith chart.
 12. The high-frequency moduleaccording to claim 10, wherein the posterior stage connection circuitincludes a branch portion branching a path connected to an inputterminal of the low noise amplifier into a path connected to a commonterminal of the first initial stage connection circuit and a pathconnected to a common terminal of the second initial stage connectioncircuit.
 13. The high-frequency module according to claim 1, whereineach of the plurality of filters includes an elastic wave resonatorusing surface acoustic waves, bulk waves, or boundary acoustic waves.14. A communication apparatus comprising: an RF signal processingcircuit that processes a high-frequency signal which is transmitted andreceived with an antenna element; and the high-frequency moduleaccording to claim 1 that transmits the high-frequency signal betweenthe antenna element and the RF signal processing circuit.
 15. Thecommunication apparatus according to claim 14, further comprising afirst impedance adjustment circuit that is connected between theconnection circuit and the low noise amplifier, wherein the firstimpedance adjustment circuit adjusts a first impedance when a circuitportion in which the first impedance adjustment circuit is connected tothe low noise amplifier is seen from output sides of the plurality offilters in a case in which the noise figure is minimum and the gain ismaximum.
 16. The communication apparatus according to claim 15, whereinthe first impedance adjustment circuit adjusts the first impedance to beany one of inductive or capacitive in both of the pass bands of thefirst filter and the second filter among the plurality of filters in thecase in which the noise figure is minimum and the gain is maximum. 17.The communication apparatus according to claim 16, wherein each of thefirst and second filters has the output impedance with a capacitiveproperty in the respective pass band of each of the first and secondfilters; and the first impedance adjustment circuit adjusts the firstimpedance to be inductive in both of the pass bands of the first filterand the second filter among the plurality of filters in the case inwhich the noise figure is minimum and the gain is maximum.
 18. Thecommunication apparatus according to claim 14, further comprising afunctional circuit that is connected between a third filter of theplurality of filters and the connection circuit and is configured orprogrammed to perform a predetermined function.
 19. The communicationapparatus according to claim 18, wherein the functional circuit is asecond impedance adjustment circuit that generates a second impedancewhen a circuit portion in which the functional circuit is connected tothe third filter is seen from an input side of the low noise amplifierclose to the matching region in a pass band of the third filter on theSmith chart.
 20. The communication apparatus according to claim 14,wherein wherein the plurality of filters include three or more filters;and each of the filters and the connection circuit are connected withoutconnecting an impedance element in each of the plurality of paths.